1. Field of the Invention
The present invention relates to an image transmission device and a storage medium with a program for realizing its function, an image display device and a storage medium with a program for realizing its function, and image transmission/reception system which are capable of preventing the image data from being tampered with and ensuring the originality.
Recently, more and more companies are taking what is called a paperless measure capturing documents, checks and the like as image data and corresponding the data by using a network system. However, the development of computer pertinent art helps the paperless measure, on the other hand, enables the image data to be easily tampered with.
2. Description of the Related Art
In the conventional paper culture, marks, stamps, signs and the like are used to ensure that the documents and checks are not tampered with, in other words, to ensure the originality. Also, a watermark is used on, for example, bills, gift certificates, official documents or the like to ensure the originality. Considering this point, some kind of measure needs to be taken to ensure the originality of documents and checks in taking the paperless measure mentioned above.
A part of image data can be easily tampered with having no visual evidence by being electronically processed. Consequently, it is difficult to ensure the originality only by putting marks, stamps, signs and the like on a part of the image data as in the conventional paper culture. Therefore, ensuring the originality is conventionally achieved by calculating a hash value from the coded-image data and by embedding an electronic watermark in the coded-image data. The hash value and the electronic watermark enable to judge whether the image data are tampered with or not in decoding the image data when even a part of the image data are tampered with.
Meanwhile, the stamps, the signs or the watermarks in the paper culture can be visually confirmed and it can be judged easily and immediately that the stamps, signs or watermarks, are not tampered with. However, when the electronic process in which the hash value and an electronic watermark are used is used, judgement cannot be easily achieved since a specific process, for example, operating a decoder is necessary to judge whether the image data are tampered with or not.
Also, in using the electronic watermark, if the algorithm for embedding the electronic watermark is analyzed, the electronic watermark might be embedded by using the algorithm after a randomly chosen image data are tampered with. Since image data with an electronic watermark embedded ensure that the image data are not tampered with, the art of electronic watermark makes it all the more difficult to detect that the image data are not tampered with.